Rotational mold for making multi-color plastic shells

ABSTRACT

Apparatus for manufacturing multiple color thin-walled hollow shells for parts such as automobile door panels, consoles and instrument panels from dry thermoplastic plastisol includes a supply box with a divider to form two or more compartments in the box. The box divider cooperates with selectively positioned split mold parts defining a separation in an open-ended heated mold for separating the mold into two or more sections. Complementary open ends of the charge box and mold are joined. Then the apparatus is rotated so that the powder is distributed into each mold section by gravity flow with the powder from each section flowing to the divider which separates the colors so as to form two or more tones on a resultant shell of cured material; thereafter the powder box is removed and the split mold parts are joined to clamp cast shell segments for fusion at a joint line.

TECHNICAL FIELD

This invention pertains to an improved plastic shell and a method andapparatus for making such articles especially suitable for use inautomobile trim components such as interior door panels and moreparticularly to two-tone plastic shells and method and apparatus forprocessing dry thermoplastic plastisol to form such articles to have twoor more tone colors and an integral joint line.

BACKGROUND ART

The automotive industry has turned to the use of interior trimcomponents such as door panels comprising a polyvinyl chloride shell.See, for example, the trim components disclosed in U.S. Pat. No.3,123,403. The acceptance of such components has been because inter aliathis type of construction permits a wide latitude in styling and color,and grain effects which are most desired particularly in the interiordesign of automobiles.

The current state of the art includes a pre-formed grained vinyl shellmade from dry thermoplastic plastisol particles which are applied to aheated shell mold from a supply box to form a continuous monochromaticone-piece shell.

In order to enhance the interior decor of an automobile, interior doorpanels and other parts have been proposed which include two separateplastic shell sections formed from different colored plastic joined by aseparate connector strip at a connection joint.

The use of multi-color plastic is also known in the manufacture ofcolored filaments. Such manufacture includes use of a compartmentedspinning head for making two-colored yarn as disclosed in U.S. Pat. No.3,049,397 issued Aug. 14, 1962 for Process of Making Space-Dyed Yarn.

Apparatus and method for multiple colored thermoplastic floor materialsare set forth in U.S. Pat. No. 3,383,442 issued May 14, 1968.

Also, the use of movable dividers in molds for molding products is knownas practiced in U.S. Pat. Nos. 1,521,316, issued Dec. 30, 1924;3,859,016, issued Jan. 7, 1975 and 4,335,068, issued June 15, 1982.

None of the aforesaid methods and apparatus for manufacture of plasticproducts is directed to a process or apparatus for manufacturing asingle piece shell product, for example, an interior panel component ofan automobile.

STATEMENT OF INVENTION AND ADVANTAGES

In accordance with the present invention a process and apparatus forloading an open-ended heated mold with powder plastisol materialincludes the process of releasing a pre-charge of two or more colors ofthermoplastic plastisol from separate compartments in charge box meansfor gravity flow into a mold of split tooling configured for movableassociation with a divider to produce a one-piece shell with two or morecolor tones to enhance the decor of the interior of an automobile.

The process includes providing an open-ended charge box with a dividermeans to form two or more separate compartments; each of which is filledwith a predetermined quantity of different color plastisol.Complementary open ends on the charge box means and on an open-endedmold are joined to form a closed system. The mold has split portionswhich are sealed with respect to the divider means to separate eachcompartment of the charge box means. The closed system is rotated sothat the charge box releases the plastisol from the separate charge boxcompartments to flow evenly through the open end of the mold by gravityand against casting surfaces on each of the split mold portions so as toproduce a uniform thin shell on each split mold portion.

The charge box and divider means are removed from the mold; thereafterthe split mold portions are joined to form a joint between theseparately cast shells.

Molding apparatus of the invention includes a gravity fill system forflow of dry plastisol material onto a heated casting surface of a moldto form a thin walled single plastic part of multi-color and for returnof excess plastisol material from the mold including charge box meanshaving a plurality of separate compartments; each of the separatecompartments adapted to be filled with a different color dry plastisoland each of the compartments extending across an open end of the chargebox means. Means are provided for coupling the box to the mold atcomplementary openings therein; split mold portions and a dividerpartition the mold to receive a single color plastic powder on each ofspaced casting surface regions on split portions of the mold; and meansare provided to operate the coupled box and mold to dispose the chargebox with respect to the mold for gravity flow of dry plastisol from eachof the separate charge box compartments onto the split portions of themold so that plastisol particles cover uniformly heated separatesurfaces on each split portion of the mold with a different coloredmaterial; and means are further provided to clamp and unclamp the splitmold portions from the divider following formation of cast shells oneach split mold portion and to clamp each of the cast shells together toform an integral joint therebetween.

Other advantages and a more complete understanding of the invention willbe apparent to those skilled in the art from the succeeding detaileddescription of the invention and the accompanying drawings thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a single-piece multi-color panel of thepresent invention shown with associated component parts of an automotivevehicle door panel;

FIG. 2 is a diagrammatically shown sectional view of a mold component ofthe inventive apparatus in association with a charge box;

FIG. 3 is a diagrammatically shown sectional view of a box of theinvention sealed to the mold of FIG. 2 in a pre-release position;

FIG. 4 is a sectional view like FIG. 3 showing the box and mold in aplastisol release orientation;

FIG. 5 is a fragmentary, enlarged sectional view of a split mold anddivider means disposed in a plastisol particle casting disposition;

FIG. 6 is a fragmentary, enlarged sectional view of the split mold partsdisposed for removal of a charge box and divider;

FIG. 7 is a fragmentary, enlarged sectional view of the split mold partsclamped to form an integral joint between previously cast shells formedon the split mold parts by partially fused plastisol particles;

FIG. 8 is a fragmentary, enlarged sectional view of an abutting jointdesign of the split mold tooling; and

FIG. 9 is a second embodiment of the joint design of the split moldtooling shown in FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

The process and apparatus of the present invention will be describedwith reference to the production of plastic thin-walled shells for atypical automotive part such as an interior door panel, console panel orinstrument panel.

FIG. 1 shows a typical automobile door panel application of amulti-color, single-piece interior plastic shell 10. The shell 10,preferably made of polyvinyl chloride material, is backed by a layer ofpolyurethane foam 12 bonded to the shell 10 by a mold process such as inU.S. Pat. No. 3,123,403, issued Mar. 3, 1964 for Automobile Arm Rest. Aninterior reinforcing insert 14 is connected at a joint 16 to an outerdoor shell 18 to form an interior space 20 for window lift mechanism(not illustrated) to raise and lower a window 22.

In accordance with the present invention the shell is a one-pieceplastic part with an integral lower panel 24 of a drycast plastic havinga first color. The shell 10 includes an integral joint 26 which is atthe base of a recessed groove 28. The groove 28 forms a transition to anintegrally formed upper panel 30 including an armrest segment 32 formedof drycast plastic having a second color contrasting or complementingthe color of the first panel 24 or other interior components. Forexample, the upper panel can be red, blue, yellow or beige to contrastwith or complement the interior color of seats, headliners, instrumentpanels and the like. The lower panel 24 can be colored a deepercomplementary tone color of a character which has a low impact or scuffdisplay character.

Referring to FIGS. 2-4, a dry plastisol molding process line isschematically shown as including selectively heated mold 34 with splitportions 35,37. A plastisol box 36 is operated between raised andlowered positions with respect to the mold 34 by suitable handlingequipment, one type of which is specifically set forth in co-pendingU.S. Ser. No. 500,760 filed June 3, 1983 for Mold Loading Method andApparatus.

The box 36 further includes an upper open end 38 which is configured tocover the planar extent of a complementary opening 40 to mold 34.

Clamp means 42 join and seal the charge box 36 to mold 34 when the box36 is elevated to the position shown in FIG. 3, hereinafter referred toas the "mold-up" position.

As a result, the interior of box 36 and the interior of mold 34 form aclosed system 44 having plastisol charges in the box 36.

In accordance with the process and apparatus of the present invention,the box 36 is provided with a divider 46 and the mold 34 has its splitportions 35,37 movable between clamping and unclamped positions to bedescribed.

The divider 46 and split portions 35,37 are in contact during plastisolcasting to form two separate compartments 50,52 each containing a chargeof plastic plastisol material of a different color (color A in 50, colorB in 52).

The casting process step includes concurrent rotation of the closedsystem 44 by drive means 53 about axis 54 defined by trunnions means ofthe type set forth in copending U.S. Ser. No. 500,760 through 180°relative to the FIG. 3 position.

At FIG. 4 a fill step of the process is shown in which dry plastisol isdistributed evenly throughout the mold opening 40. A resultant evenbuild-up of cast plastisol occurs on pre-heated casting surfaces 56,58on the split portions 35,37, respectively, of the mold 34. The moldposition shown in FIG. 4 will hereinafter be referred to as the"mold-down" position.

Following the fill step, the joined mold 34 and charge box 36 are againrotated 180° by the drive means so that the mold 34 is locatedvertically above the box 36 in the mold-up position.

An air-jet system of the type shown in the co-pending U.S. Ser. No.500,760 may be used to dislodge excess plastisol from the walls of themold by the drive means so that the dislodged material will flow bygravity return to the interior of the box for collection and reuse inthe system.

A plastisol fuse cycle is then carried out in accordance with knownpractice wherein the plastisol particles are partially fused as athin-walled part. The charge box is unclamped from the mold 34 and thesplit portions 35,37 are separated by a space 60 so that the divider 46as shown in FIG. 6 and the box 36 can be removed from the mold andreturned to a plastisol make-up position. Thereafter the mold splitportions 35,37 are clamped with the plastisol cast to the surfaces 56,58being forced together when partially fused. The unit is heated furtherto finally fuse the plastisol, then is cooled and rotated 180° into astrip position corresponding to the mold-down position. Make-upplastisol of appropriate color is fed to the multiple separate colorcompartments.

In accordance with the present invention, the split portions 35,37 anddivider 46 are specially configured and sequentially, operativelypositioned to produce an integral joint between plastisol cast on therespective surfaces 56,58. More specifically, as shown in FIG. 2, thesplit portions 35,37 have spaced supports 60,62 and 64,66, respectively,fixed thereto. Each of the supports 60-66 carry a bearing 68 that isslidably supported on a guide rod 70 which is supported to a moldsupport 71. A reciprocating drive unit 72 has its drive shaft 74 coupledto split portion 35 to reciprocate it through clamping and unclampingmovements on rod 70 with respect to split portion 37. Likewise, areciprocating drive unit 76 has its drive shaft 78 connected to splitportion 37 to reciprocate it through clamping and unclamping movementson rod 70 with respect to split portion 35.

In FIG. 2, the portions 35,37 are moved into a first unclamped positionwhich defines the opening 79 between a surface 80 on bent edge 82 ofportion 37 and a straight edge 83 on portion 35. The opening 79 is sizedto receive a bent end 84 of the divider 46 as the mold 34 and box 36 areinitially joined.

Once the bent end 84 is positioned in the opening 79, the portions 35,37are moved by drive units 72,76 through a clamping movement in which edge83 engages the bent end 84 at surface 86 and a surface 88 on bent end 82engages an inboard surface 90 of end 84; all of the aforesaid surfaceinterfaces cooperating to form the plastisol casting clamping positionof FIG. 5. In this position, the divider end 84 separates plastisolparticles A cast on surface 56 from plastisol particles B cast onsurface 58.

Once the plastisol is cast, the mold 34 and box 36 return to the FIG. 3position. As shown in FIG. 6, the mold is positioned in an unclampedposition which separates the split portions 35 and 37 to form theopening 79 for removing the divider 46 from the mold.

Partially fused particles of plastisol define layers 92,94 on thecasting surfaces 56,58 on the separated split portions 35,37. The splitportions 35,37 are then moved through a clamping movement which causesthe layer 92 to be joined and clamped to layer 94, as shown in FIG. 7.The layers 92,94 are folded and/or pushed together and are finally fusedto form a folded joint in a unitary, one-piece product.

Two typical joint-line sections are shown in FIGS. 8 and 9. FIG. 8 showsan abutting joint. In this configuration the net tooling closure line 96is disposed approximately midway of a plastisol layer 98 formed on thesurface 80 of bent end 82. The end 100 of a layer 102 formed at thestraight end 84 is thus abutted into and clamped to the layer 98 to forman L-shaped joint 104 therebetween.

In FIG. 9 a compression mortise joint is shown. It is formed by locatingthe net tooling closure line 108 at the surface 80 on bent end 82. Also,there is a vertical offset of the casting surfaces 56,58 so that aplastisol layer 112 cast on surface 56 will form a straight line joint114 with respect to the plastisol 116 formed on surface 80 of bent end82.

A typical powder casting process for a two-color door panel includes thefollowing sequence.

1. Preheat tool in oven to temperature between 250° F. and 390° F.

2. After mold cast temperature is reached, attach the powder box to themold.

3. Rotate box and mold.

4. Dwell time on top (for part thickness).

5. Rotate 180° and unclamp.

6. Clamp the split mold parts to join partially fused separate shellsand return the mold to the oven for cure.

Examples of suitable mold heating processes for use with the process andapparatus of the present invention include mold temperature control byheated and cooled air or oil heating and cooling flow as set forth inU.S. Pat. No. 4,217,325 issued Aug. 12, 1980 to D. Colby. Suitablethermoplastic plastisol particles include plasticized polyvinylchlorides and related vinyl resins in dry form for ease of gravity flowfrom the charge box 36 during both fill and return steps. Typicalexamples of parts, plastic materials and mold processes include thefollowing:

Examples of parts that have been made by the dry PVC cast moldingprocess include a door panel shell having a mold volume of approximatelysix (6) cubic feet.

PVC resin, plasticizer, stabilizer, release agents and color pigmentsare combined in a high intensity mixer to produce a dry, flowable powderof each desired color. The process is known in the industry asdry-blending.

The various compound components may be selected as to type and ratio toprovide the properties required both for the finished product and forease of processing. Physical properties will not be too dissimilar fromthose obtained with liquid plastisol which is also used to manufacturesimilar products but has an inherent weakness for forming objectionabledrips and runs when made in complex shapes.

Processing properties are such that when melting of the plastic powderoccurs, densification results in exact reproduction of minute detailsuch as grain marks and stitches engraved in the mold surface.

Mold preheating temperature may range from 250° F. to 390° F. Since thethickness of the finished product is also governed by the time theplastisol particles contact the mold, it should be understood thatsimultaneous charging of the particles to the solit mold portions can beof definite advantage. Also, if certain areas of the mold can be made tohave a lower pre-heated temperature than others, it will permit moldinga thinner shell in those areas, since both temperature and mold-filledtime determine the final thickness of the shell. Therefore, a veryflexible range, for mold-filled time, of one second to ten seconds ormore has been established.

Depending on formulation, final melting or fusion of the PVC powderoccurs when mold temperatures reach 350° F. to 450° F.

After final fusion, the mold is cooled to a temperature which willfacilitate removal of the shell without damage.

Specifically the process and apparatus of the present invention enableeven and complete distribution of thermoplastic plastisol material ontomold surfaces to form large, long, thin-walled single-piece two-color ormore shells for interior door panels and the like formed during shortcycle mold cycles in limited plant floor space.

While representative embodiments of apparatus and process of the presentinvention have been shown and discussed, those skilled in the art willrecognize that various changes and modifications may be made within thescope and equivalency range of the present invention.

What is claimed is:
 1. Apparatus for molding a thin-walled plastic shellin a heated open-ended mold from a charge of dry thermoplastic plastisolmaterial in open-ended charge box means comprising: means for joining amold and charge box in open-ended relationship; co-acting means on thecharge box and the mold to define at least two separate casting surfaceson the mold; means for rotating the mold and charge box so as todistribute two charges of different color against the separate castingsurfaces of the mold;said charge box including a single open-end boxhaving a divider separating the box into first and second open endcompartments each having a predetermined charge of plastic powder ofdifferent color; said mold having first and second separable splitportions movable to clamp and unclamp the divider to define the firstand second power casting surfaces on the split portions for receivingpowder from the first and second open end compartments when the box andmold are joined and rotated; and joint formation means including a bendend on one of said split mold portions engageable with said divider whenin clamped position to form a powder collection region.
 2. In thecombination of claim 1, means for unclamping said split portions of saidmold from the divider to permit separation of said charge box and fromsaid mold, and means for clamping said split portions to cause separateplastisol shells cast thereon to be finally fused to form an integraljoint between such shells.